Multiple scattering in the remote sensing of natural surfaces
- Univ. of Washington, Seattle, WA (United States)
Radiosity models predict the amount of light scattered many times (multiple scattering) among scene elements in addition to light interacting with a surface only once (direct reflectance). Such models are little used in remote sensing studies because they require accurate digital terrain models and, typically, large amounts of computer time. We have developed a practical radiosity model that runs relatively quickly within suitable accuracy limits, and have used it to explore problems caused by multiple-scattering in image calibration, terrain correction, and surface roughness estimation for optical images. We applied the radiosity model to real topographic surfaces sampled at two very different spatial scales: 30 m (rugged mountains) and 1 cm (cobbles and gravel on an alluvial fan). The magnitude of the multiple-scattering (MS) effect varies with solar illumination geometry, surface reflectivity, sky illumination and surface roughness. At the coarse scale, for typical illumination geometries, as much as 20% of the image can be significantly affected (>5%) by MS, which can account for as much as {approximately}10% of the radiance from sunlit slopes, and much more for shadowed slopes, otherwise illuminated only by skylight. At the fine scale, radiance from as much as 30-40% of the scene can have a significant MS component, and the MS contribution is locally as high as {approximately}70%, although integrating to the meter scale reduces this limit to {approximately}10%. Because the amount of MS increases with reflectivity as well as roughness, MS effects will distort the shape of reflectance spectra as well as changing their overall amplitude. The change is proportional to surface roughness. Our results have significant implications for determining reflectivity and surface roughness in remote sensing.
- OSTI ID:
- 255311
- Report Number(s):
- CONF-960203-; CNN: Contract 958450 (SIR-C); Contract NASA 5-31372; TRN: 96:002806-0011
- Resource Relation:
- Conference: 11. thematic conference on geologic remote sensing, Las Vegas, NV (United States), 27-29 Feb 1996; Other Information: PBD: 1996; Related Information: Is Part Of Proceedings of the eleventh thematic conference - geologic remote sensing: Practical solutions for real world problems. Volume 1; PB: 634 p.
- Country of Publication:
- United States
- Language:
- English
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